Formula Storage Guidelines

Prepared infant formula doesn’t stay safe indefinitely — it needs to be used, refrigerated, or discarded within specific windows. Here’s what U.S. federal guidance says about storing formula safely, from mixing to feeding time.

The CDC recommends using prepared formula within 1 hour from the start of feeding and within 2 hours of preparing it, and the FDA gives the same 2-hour room-temperature limit. If you’re not using prepared formula right away, refrigerate it immediately and use it within 24 hours. Any formula left in the bottle after your baby has fed from it should be thrown away, since it now contains saliva that can encourage bacterial growth. This guide covers formula only — breast milk storage times are different and covered in our separate Breast Milk Storage Guide.

Mixing and Preparing Formula Safely

For powdered formula, the CDC recommends using water that’s been brought to a boil and cooled for no more than 5 minutes, then adding the formula powder while the water is still hot enough to help kill germs that can be present in powdered formula. Let the prepared bottle cool to a safe temperature — testing it on your wrist — before feeding.

Powdered infant formula is not sterile. Liquid, ready-to-feed formula is manufactured to be sterile, which is why the CDC notes it’s a lower-risk option worth considering if your baby is at higher risk of severe illness — talk to your pediatrician about whether that applies to your baby.

Storage Time Limits at a Glance

Prepared formula at room temperature: use within 2 hours of preparing (and within 1 hour of when feeding starts, per CDC guidance)
Prepared formula, refrigerated promptly: use within 24 hours
Formula your baby has started drinking from: discard any leftover amount — do not refrigerate or reuse it
Opened liquid concentrate or ready-to-feed containers: follow the manufacturer's printed storage instructions on the container, which can vary by product

Never save and reuse formula left over from a feeding, even if it looks untouched. The FDA warns that saliva introduced during feeding lets bacteria multiply, and that risk isn’t eliminated by refrigerating the leftover formula afterward.

Why the Time Limits Exist

These limits exist because bacteria — including Cronobacter, a germ the CDC specifically warns can be present in powdered formula — can multiply in prepared formula that sits at room temperature or is stored too long, even in the refrigerator. Infants have less mature immune systems than older children and adults, which is why federal guidance treats formula more conservatively than many other foods.

If you’re traveling or don’t have reliable refrigeration, consider single-serve ready-to-feed formula, which doesn’t require mixing and can be fed directly, or prepare only what your baby is likely to finish in one feeding to avoid waste and storage guesswork.

Sources

This guide is based on published guidance from the U.S. Food and Drug Administration (“Handling Infant Formula Safely: What You Need to Know”) and the Centers for Disease Control and Prevention (“Preventing Cronobacter in Infants”). It’s provided for general education — always follow the preparation and storage instructions printed on your specific formula’s packaging.

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